This paper considers, from a naval perspective of Japan-USA alliance, the significance of Japan-U.S. security arrangements in light of the new security environment characterized by the collapse of the former Soviet Union, which was their common strategic focus throughout the Cold War, and the resulting unipolar power structure, proliferation of weapons of mass destruction, and international terrorism. In concrete terms, the author proposes that anti-submarine warfare capabilities, in which JMSDF excels in regional waters, and the capabilities of U.S. Navy has let diminish, will serve as a bonding agent to create a new Japan-USA strategic posture which complements each other.